The invention generally relates to an indicator for thermoplastic roofing membranes and more specifically to a temperature sensitive indicator disposed on the upper surface of an overlapping roofing membrane which indicates that the adjacent, overlapping membranes have been subjected to a sufficiently high temperature to achieve a proper seal between them.
Within the last decade, elastomeric and thermoplastic roofing membranes have become significant products in the commercial and industrial marketplace. They provide good service life on flat and low slope roofs while representing a cost effective alternative to built up roofs and other previously available roofing systems. Roofing membrane products are typically manufactured as elongate sheet goods having a width of 3 feet (0.9 meters) or greater which are provided in rolls. The membrane is unrolled on a roof with edge adjacent portions of the membranes overlapped on the roof surface. The overlapped regions are then sealed together.
In order to achieve their service and cost saving potential, the elastomeric and thermoplastic roofing membranes must be continuously and tightly sealed along these overlapping regions. Typically, the overlapping regions are sealed by heating the adjacent surfaces of the overlapping membranes and then pressing the heated surfaces together, merging the material of the membranes and providing a strong seal. The integrity of the seal and thus of the overall roof depends upon appropriate and sufficient heat application to achieve melting of the membrane material and a positive, continuous seal between the overlapping membranes.
One approach to ensuring a membrane-to-membrane seal is the intentional excess application of heat. While this may achieve a seal, it is generally slow as the application of larger quantities, i.e., excess, heat takes longer than the application of the appropriate amount of heat. More importantly, however, excess heat application may result in damage to the roofing membranes which will ultimately shorten their service life. Furthermore, such an approach is energy inefficient. This approach has thus generally been found to be unsatisfactory.
Another approach to ensuring seal integrity involves checking, either visually or mechanically and either on a spot or continuous basis, the seal by manually lifting the edge of the upper membrane to determine if it is properly secured to the lower membrane. Obviously, spot checks can miss unexamined unsealed areas and continuous inspection of every seam is time consuming and therefore costly.
From the foregoing, it is apparent that a means for providing an indication of proper heat exposure and thus proper sealing of a membrane roofing seam would be highly desirable.